MASTER GARDENER: Does a Plant Know Anything? Part 2

Daniel Chamovitz’s’ book, "What a Plant Knows" is a fun and interesting read and this article sums up the second half of his book giving us insight into what a plant “smells, “hears” and “remembers."

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Editor's note: This is part two of Helenruth's segment on understanding what a plant knows. Click here to read part one.

Daniel Chamovitz’s’ book, "What a Plant Knows" is a fun and interesting read and this article sums up the second half of his book giving us insight into what a plant “smells, “hears” and “remembers."

Plants smell. They emit odors and also sense their own odors and those of neighboring plants.

A plant’s range for smell is limited, but it is highly sensitive and communicates a great deal of information to the living organism through its perception of odor or scent through stimulus. What odors does a plant perceive, and how do smells influence a plant’s behavior?

In 1924, Frank E. Denny from the U.S. Department of Agriculture demonstrated that treating any fruit with ethylene gas is enough to induce ripening. A plant detects some ethylene in the air and it softens up.


Ethylene is the universal plant hormone responsible for fruit ripening and all fruits emit this organic compound. Ethylene signaling between fruits evolved as a regulator of plant responses to environmental stresses such as drought and wounding and is produced naturally throughout the life cycle of all plants.

Ethylene is particularly important for plant aging as it is the major regulator of leaf aging which gives us autumn foliage.

There is now proof through scientific research that trees release chemicals to warn neighboring trees to produce chemicals to ward off imminent insect attacks.

They sense (smell) the chemicals and emit protection. Many other plants use their own leaves when attacked by insects or bacteria to release odors that warn brother leaves to protect themselves.

So if plants can “smell” in their own unique ways without olfactory nerves, is it possible they can “feel” as well without sensory nerves?

Plants are exposed to multiple touch stresses such as wind, rain, and snow, and animals regularly come into contact with many of them. A plant feels what type of environment it lives in and adapts.

For example, it uses growth slowing to protect itself from violent winds. While plants feel touch, they don’t feel pain, panic, fear or sadness which humans may associate with touch. But plants feel mechanical stimulation and they can respond to different types of stimulation in unique ways.

And as for hearing according to this author, "The audible signals we’re used to in our world are irrelevant to a plant."


Plants lack the structures for purposeful focalization and the sounds of leaves in the wind or branches cracking under our feet do not communicate anything to the plant. The nearly 400,000 species of plants on earth have conquered their habitat without ever hearing a sound.

As we have seen through this article plants clearly have the ability to retain past events and to recall this information at a later period for use in their development. Tobacco plants know the color of the last light.

Willow trees know if their neighbors have been attacked by caterpillars. These examples, and many more, illustrate a delayed response to a previous occurrence, which is a key component of memory.

Mark Jaffe, a scientist who published one of the first reports of plant memory in 1977, referred to it as one to two hour retention of the absorbed sensory information the plant has. Plants clearly have the ability to store and recall biological information.

And the final question the author asked was, “Are plants aware?” Plants are acutely aware of the world around them. They are aware of their visual environment; they differentiate between red, blue, far-red, and UV lights and respond accordingly.

They are aware of aromas around the and respond to small amounts of volatile compounds in the air. Plants know when they are touched and can distinguish different touches.

They are aware of gravity: they can change their shapes to ensure that shoots grow up and roots grow down.

And plants are aware of their past: they remember past infections and conditions they’ve weathered and then modify needs based on these memories.


I highly recommend Daniel Chamovitz’s book, "What a Plant Knows." It gave me a “plant perspective.”

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